Novel properties of metal halide perovskite nanostructures: from quantum dots to chiral nanoclusters and carrier spin dynamics
Prof. Jin Zhong Zhang
University of California, USA
Biography：
Jin Zhong Zhang received his B.Sc. degree in Chemistry from Fudan University, Shanghai, China, in 1983 and his Ph.D. in physical chemistry from University of Washington, Seattle in 1989. He was a postdoctoral research fellow at University of California Berkeley from 1989 to 1992. In 1992, he joined the faculty at UC Santa Cruz, where he is currently distinguished professor and chair of chemistry and biochemistry. Zhang’s recent research interests focus on design, synthesis, characterization, and exploration of applications of advanced materials including semiconductor, metal, and metal oxide nanomaterials, particularly in the areas of solar energy conversion, solid state lighting, sensing, and biomedical detection/therapy. He has authored 450 publications and four books. Zhang is currently executive editor for JPCL and associate editor for ACS Physical Chemistry Au published by ACS. He is a Fellow of AAAS, APS, RSC, and ACS. He is the recipient of the 2014 Richard A. Glenn Award of the ACS Energy and Fuel Division.
Abstract:
Size is a critical factor in determining properties of materials, both quantitatively and qualitatively. In our study of metal halide perovskite nanostructures, we found some interesting fundamental changes in properties when the size is varied from >4 nm for perovskite quantum dots (PQDs) to <2 nm for perovskite magic sized clusters (PMSCs) and even slightly smaller ligand-assisted metal halide molecular clusters (MHMCs) with much stronger quantum confinement effect (QCE), as exemplified by cesium lead bromide (CsPbBr3) and methylammonium lead bromide (CH3NH3PbBr3). Besides the expected blue shift in absorption and emission with decreasing size due to QCE, the photoluminescence quantum yield and excited state lifetime decrease generally with decreasing size, attributed to increased surface defects as well as changes in the electronic band structure with size. In addition, both the PMSCs and MHMCs are found to exhibit intrinsic chiral property based on circular dichroism (CD) spectra while the corresponding PQDs do not. Possible explanations for the origin of the chirality include asymmetry induced by liquid-liquid or liquid-solid interfaces. Chiral nanoclusters are potentially useful for emerging technologies including spintronics and spin-optronics. Furthermore, we compare carrier spin dynamics of these nanostructures determined using ultrafast laser techniques and found major effects of size, phonon, nuclear spin, and surface in their lifetimes attributed to different spin relaxation mechanisms.
报告时间：2025年7月23日 9:00
报告地点：五室三楼大会议室